1. Field of the Invention
The present invention relates generally to connectors, and more particularly, to latching devices for electrical connectors.
2. Related Art
The use of electrical connectors is common and well known. Electrical connectors generally comprise nonconductive housings in which one or more electrically conductive terminals are mounted. The terminals are mechanically and electrically joined to conductive leads, such as wires, cables or conductive areas on a circuit board. The type of terminals used in electrical connectors takes on many forms, such as pairs of pins and sockets. Electrical connectors are employed in mateable pairs, wherein the respective housings and terminals in a pair of electrical connectors are mateable with one another. Thus, for example, a pair of electrical connectors may be used to electrically connect the conductors of a cable and the printed circuits on a printed circuit (PC) board, or the conductors of two cables, or the printed circuits of two PC boards.
Electrical connectors may include some type of latching means for securely but releasably retaining the pair of electrical connector housings in a mated condition. Various requirements are found in electrical connection systems for retaining housing parts together.
Conventional techniques to securely but releasably retain a pair of electrical connectors in a mated condition include the use of screws, latching arms, molded plastic housings, spring arms, and over-center latching mechanisms, to name a few. These conventional latching techniques generally work well in securing the two mating components together. However, as will be discussed below, these conventional approaches do not sufficiently prevent unparallel mating of the connector housings. Secondly, they do not prevent damage from occurring to the cables, PC boards, or pins in high insertion force applications, nor do they prevent overstressing due to either twisting or overcompression of the connector housings. Thirdly, they do not prevent the partial mating of connectors. Finally, some conventional latching means only provide a means for engaging, not disengaging, the two connector housings.
In addition to these specific operational drawbacks, many of the conventional latching techniques can only be used with only a single application, i.e., PC board to PC board, cable to cable, or cable to PC board. These and other drawbacks of conventional latching techniques are described below.
The improper installation of electrical connectors has long be a problem in assemblies containing interconnected electrical circuits. Even though the specific electrical connector can perform adequately under normal circumstances, open circuit conditions can occur when electrical connectors are not properly mated.
In addition to open circuits, which result from improper installation, terminal and connector retention are also important due to potential problems encountered over the life of the particular device. For example, excessive vibration over time can cause one connector to disengage from its associated connector. Furthermore, improper retention of contact terminals and connectors can result in unstable electrical interfaces which can result in corrosion, thus leading to a gradual deterioration of the electrical interconnection.
Many electrical connectors are used in environments where they will be repeatedly connected and disconnected by field technicians and other personnel. Some of these users have relatively little familiarity with the mechanics or intended use of the connector. It is not uncommon for field technicians to have inadequate training on the proper usage of every electrical connector they are likely to encounter. This lack of familiarity with the electrical connectors can result in overstressing the latch mechanisms employed to lockingly but releasably retain electrical connector housings in a mated condition. It is not uncommon, for example, to have inexperienced field personnel to unintentionally bias a latch mechanism too far, thereby breaking or reducing the effectiveness of the latch.
One conventional technique which has been employed in latching mechanisms to minimize this potential for overstressing the connector housing and latching mechanism has been the utilization of a latching arm. For example, U.S. Pat. No. 4,462,654 to Aeillo shows a latch mechanism integrally and pivotally connected to an electrical housing. The forward end of the latch extends from the pivoted connection to define a latch portion which is engageable with a corresponding structure on the associated mateable housing. The rearward end of the latch member extends in the opposite direction from the pivot and includes an overstress stop which is pivotable into a lug or wall on the electrical connector housing. Contact between the overstress stop and the lug or wall of the electrical connector housing is intended to limit the amount of rotation around the pivot point during the normal engagement of the electrical connector housings. This approach controls the amount of pivoting during proper use of the electrical connector. However, it does not provide positive antistress protection adjacent to the forward end of the latch member. Thus, inexperienced field personnel may apply rotational pressure to the forward most end of the latches for either locking or releasing the electrical housings to one another. Such rotational forces exerted on the forward end of the latch member may overstress the latch, thereby causing the latch to break or be of reduced effectiveness.
Another problem with the conventional latching techniques for electrical connectors is their inability to prevent unparallel mating of the connector housings. For example, some conventional techniques utilize screws as a means for maintaining the connectors in engagement to prevent separation due to excessive vibration. These screw-type latching mechanisms are configured to be adjusted either by hand or by tool. Although these techniques securely hold the two mateable electrical connector housings together, they do not prevent the connectors from being mated or separated in an unparallel fashion. In addition, in order to latch or unlatch the mating components, one has to rotate the screw through numerous revolutions in order to completely separate the two connector housings.
Many applications require the mateable terminals and associated electrical connectors to be specifically designed to achieve substantial contact forces against one another in their fully mated condition. These necessary contact forces can result in significant insertion forces during mating and unmating, particularly as the number of terminals in a connector increases. These high insertion forces may potentially damage the surface mount components or printed circuits if one or both of the mating components is a PC board. High insertion forces may also cause damage to the terminals of a cable connector.
The existence of high insertion forces also creates the possibility that the person who mates the electrical connectors will not be completely mated. Incomplete insertion of mated connectors typically will yield less than specified contact forces between the mated terminals and can result in poor electrical performance or unintended separation of the partly mated connectors. This may result in problems similar to those discussed above in relation to electrical connectors having poor connector retention.
To help insure complete insertion and to prevent unintended separation of mateable connectors, many electrical connector housings are provided with interengageable locks. In particular, one connector may comprise a deflectable latch while the opposing mateable connector may comprise a locking structure for engagement by the latch. Most conventional connectors with deflectable latches and corresponding locking structures can lockingly retain connectors in their mated condition, but require complex manipulation to achieve mating or unmating. The above-described high insertion forces in combination with the manipulation required for the locking means in conventional connectors can make mating and unmating particularly difficult.
Some conventional approaches include ramped locking structures which are intended to assist in the complete insertion of the connectors. In particular, many conventional approaches include connectors wherein a deflectable latch on one connector and a corresponding locking structure on the mateable connector are constructed such that the resiliency of the latches and the angular alignment of the ramp cooperate to urge the connectors toward a fully mated condition. Examples of electrical connectors with this general construction are shown in U.S. Pat. No. 4,026,624 to Boag and U.S. Pat. No. 4,273,403 to Cairns. In these connectors, the unmating is rendered difficult by the need to overcome both, the contact forces in the terminals and the ramping forces in the latches of the housing. Therefore, although these latches facilitate the mating of the connectors, they require substantially greater forces in unmating. As a result, two hands are required. Also, these greater forces sometimes cause the user to pull at the cables rather than the connector housings and latches.
A similar type of conventional connector includes the use of a spring-arm instead of a ramped locking structure mentioned above. For example, U.S. Pat. No. 4,941,849 shows a shielded electrical connector having a latching mechanism comprising an outer insulating cover which is profiled to overlap and encompass an inner shielded connector sub-assembly. The outer housing of the electrical connector has a pair of spring-arms hinged to it which are spring loaded into a position where the forward section of the spring-arm is proximate to the side walls of the shielded sub-assembly. The forward section of the spring-arm includes a rearwardly directed latching face, which is latchable to a complementary latching structure and a complementary connector. The outer insulating housing member includes windows along the sidewalls such that when the outer housing overlaps the inner shielded sub-assembly, actuator arms of the inner spring members extend outwardly through the windows of the outer housing members.
To unlatch the connectors, the spring-arms are compressed toward the shielded inner sub-assembly causing the spring-arms to rotate about their hinged position thereby moving the forward section, including the rearwardly facing latch, outwardly to a position where the connector assembly is adequate for its intended purpose. A disadvantage of this connector design is that two separate movements must be made prior to unlatching the connector. The latching arms must be compressed and the connector housings must be pulled rearwardly to unlatch the connector assembly.
Another problem of conventional electrical connectors is referred to in the art as "fish-hooking." In particular, the latch members on many electrical connectors are cantilevered structures that effectively function as fishhooks which may catch insulated leads as the electrical connector is being inserted into or removed form an electrical apparatus. Fish-hooking can damage an adjacent circuit that is unintentionally caught by the latch structure of the electrical connector housing. Additionally, an attempt to latch or unlatch structure while a wire or other lead is in its fish-hooked engagement can permanently damage the electronic device.
Often, electrical connectors and their latching means are constructed as a single integral unit. The housing and latch structures are commonly molded from the same plastic material. However, all plastics will eventually be deformed or yield their shape when submitted to a continuous load. This is particularly true for nylon, which loses its resiliency over time or temperature. Accordingly, conventional latching mechanisms made of plastics lose their effectiveness over time for assisting in the continued retention of the connector housings.
What is needed is a latching device that can be used with multiple configuration, e.g., PC board to PC board, PC board to cable, and cable to cable. These latching devices must be able to latch and unlatch connectors in a parallel fashion and remove or absorb the high-linear insertion force required in some applications. In addition, the latching devices must be able to protect the electrical terminals and printed circuits of the mating devices by preventing overstressing, either by twisting or overcompression. Also, what is needed is a parallel latching device which will provide the user some indication or provide some guarantee that the connector housings are in their fully mated position.